The invention relates to the cooling of electronic components and, in particular, to the cooling of electronic components mounted on a circuit board.
The speed of electronic components steadily accelerates and, at the same time, increase in density. Additionally, more components are often placed within a single housing than ever before. All these factors; increased speed of operation, increased density of circuitry within a component, and the increased density of components within a housing, contribute to higher operating temperatures. As the temperature of electronic components increase, their reliability decreases. Heat equals failure and it must be dissipated in order to ensure the proper operation of systems that employ components. Various approaches to the cooling of electronic components have been pursued. Forced fluid cooling is described, for example in, U.S. Pat. No. 4,851,965 issued to Garbuzda et al (Garbuzda), which is hereby incorporated by reference. Garbuzda describes the use of jet impingement of air onto the heat generating component through separate plenums. A circuit pack with inboard jet cooling is described in U.S. Pat. No. 5,067,047 issued to Azar, which is hereby incorporated by reference. It has also been suggested that air can be blown onto the components through holes in the enclosures or shields surrounding the circuit components (see for example, U.S. Pat. No. 4,393,437 issued to Bell et al and U.S. Pat No. 4,408,255 issued to Adkins, both of which are hereby incorporated by reference. It has been suggested that holes in the circuit boards themselves could allow air to impinge on components in circuit packs which are stacked (see, for example, U.S. Pat. No. 4,399,484 issued to Mayer which is hereby incorporated by reference).
Although effective in some ways, each of these approaches has its own limitations. An electronic cooling system that provides efficient and substantial cooling potential for electronics systems would be highly desirable.
A circuit board cooling system in accordance with the principles of the present invention includes a xe2x80x9cfillingxe2x80x9d of thermally conductive material sandwiched between two circuit boards. The term xe2x80x9cthermally conductive materialxe2x80x9d is used herein to include a variety of materials, such as copper, aluminum, copper alloys, and other materials known in the art. The thermally conductive element of this thermal sandwich conducts heat away from both of the attached circuit cards. The thermally conductive extent may be a solid slab of thermally conductive material, such as copper, it may be a hollow, substantially planar thermal conductor with an internally circulating cooling fluid, or it may be a substantially planar heat pipe, for example. The circuit boards attached to either side of the thermally conductive element may be attached with both board""s wiring sides in direct contact with the thermally conductive element, with both board""s component sides in direct contact with the thermally conductive element, or with one board""s component side and another board""s wiring side in contact with the thermally conductive element. On or more cavities may be fashioned in the thermally conductive element to accommodate electronic components. The cavities may completely pierce the thermally conductive element, or they may form a well, or depression, in a surface of the thermally conductive element.
Although circuit boards are typically coated with a dielectric material, or potted, to prevent electrical shorts, in order to ensure that the thermally conductive element does not short any circuits on the circuit cards, additional dielectric material may be placed on the surfaces of the thermally conductive element that make contact with the circuit boards. A xe2x80x9cthermal greasexe2x80x9d may be employed to form a good thermally conductive interface between the thermally conductive element and at least one of the attached circuit boards.